Tuesday, October 26, 2021

Survival of Stocked Trout in Tailwaters

 


I received an email the other day from one of my fly fishing buddies concerning stocked rainbow trout in the Sipsey Tailrace that we fish. The email contained a study conducted by an Auburn University student in partial fulfillment for a Degree of Masters in Science. 

Hypolimnetic discharge waters (the layer of water in a thermally stratified lake that lies below the thermocline, is noncirculating, and remains perpetually cold)  from reservoirs in the southern U.S. provides water temperatures cold enough to support Rainbow Trout fisheries in regions where they otherwise could not exist. The Sipsey Fork tailwater in Alabama provides such an opportunity and is stocked with Rainbow Trout monthly. In a recent survey, less than 25% of the Rainbow Trout stocked each month were harvested and few trout appeared to persist in the system for more than 3-4 weeks. The objective of this study was to describe post-stocking dispersal and the fate of the non-harvested Rainbow Trout. In March, June, and October 2017, and January 2018, numerous Rainbow Trout were radio-tagged and tracked to document movement patterns and to determine longevity in the tailrace. Tagged Rainbow Trout had dispersed an average of 4.1 km or 2 .54 miles with only 30% of tagged Rainbow Trout remaining alive five weeks after stocking. The extent of predation on Rainbow Trout was assessed using a bioenergetics approach. Electrofishing surveys and diet analysis of predators identified Striped Bass as the primary predators of Rainbow Trout in the Sipsey Fork. Bioenergetics simulations revealed that approximately 500 Striped Bass living continuously in the tailwater from March through October could consume all Rainbow Trout stocked each month. Knowledge regarding the dispersal and fate of stocked Rainbow Trout in this system can improve the management of the fishery.


This study proves what a lot of us who fish the tailrace have known for some time that the Striped Bass consumes a large number of the trout once they move beyond the pump station. I have never seen Striped Bass above the pump station which is where a lot of the fly fishermen wade. All the guide trips take place above the pump station. There is less than a quarter of a mile of prime trout fishing from where the trout are released to the pump station. The rest of the tailrace is much too deep to wade. I feel the deep water below the pump station is where most all the trout are consumed by Striped Bass. 1100 to 1200 pounds of trout are released in the tailrace each month which could equal to 1000 trout or below depending on the size of the trout. Consider how many trout would be left in the quarter-mile wading section if trout were released every couple of months.

I respect the findings of this study but see little chance of reversing the effects the Striped Bass have on trout that is stocked in the Sipsey. 

6 comments:

Justin said...

Hi Bill. Fascinating! How big are the striped bass? What if a larger size trout was released? They do something similar here, stocking trout large enough to avoid being swallowed by cormorants. Thanks for the interesting note.

Brk Trt said...

Bill stocked trout are very necessary in the world we fish in today. They provide the fly fishing experience to many that would never know the joy of landing a trout on a fly. But they will never match the performance of wild trout.

Rainbows are easily bred and grow pretty rapidly in hatcheries. This enables them to be stocked several times through out the year. I think brown trout would be better to stock if long term survival is needed.

Mark Kautz said...

Once again I apparently missed this post although I think the problem is that they just don't show up on my blogroll for a day or two, because I look every day. That said, I assume the Sipsey flows into a lake where the Striped Bass come from. They seem to know when the trout are stocked and come to dinner during that time. It also seems that they can't get above the pump station or I'm sure they'd be feasting up there too. Good post.

Bill Trussell said...

Justin
The Striped Bass are huge in the 20 lb weight range and can consume a lot of trout in the size of 10 inches. They release some trout over the 16" mark but not many of them stay in the wading area of the tailrace. Thanks for the comment

Bill Trussell said...

Mark
The Striped Bass are native to the tailrace and have been there for years and yes they love to eat the trout! Thanks for the comment

Bill Trussell said...

Alan
I totally agree; I am glad we have a place to fish for trout here in Alabama and the trout are stocked once a month in the Sipsey. Thanks for the comment